ABSTRACT
The development of a new method for glycosylation with 1-hydroxy glycosyl donors employing dialkyl sulfonium reagents is described. The process employs the reagent combination of a dialkyl sulfide and triflic anhydride to effect anomeric bond constructions. This controlled dehydrative coupling of various C(1)-hemiacetal glycosyl donors and nucleophilic acceptors proceeds by way of a sulfide-to-sulfoxide oxidation process in which triflic anhydride serves as the oxidant.
Subject(s)
Safrole/analogs & derivatives , Safrole/chemistry , Sulfides/chemistry , Glycoconjugates/chemical synthesis , Glycosylation , Oligosaccharides/chemical synthesis , Oxidation-Reduction , Water/chemistryABSTRACT
[figure: see text] Direct synthetic access to 2-hydroxy-alpha-mannopyranosides from glucal donors is accomplished via a one-pot stereoselective oxidative glycosylation reaction, employing the reagent combination of dibenzothiophene bis(triflate) and dibenzothiophene-5-oxide.
Subject(s)
Monosaccharides/chemistry , Monosaccharides/chemical synthesis , Carbohydrate Conformation , Disaccharides/chemical synthesis , Disaccharides/chemistry , Indicators and Reagents , Molecular Structure , Oligosaccharides/chemical synthesis , Oxidation-Reduction , StereoisomerismABSTRACT
[reaction: see text] The synthesis of a selectively protected form of the bicyclic guanidine fragment of batzelladine A from L-aspartic acid is reported, thereby establishing the absolute configuration of the bicyclic guanidine ring system within the natural product.
Subject(s)
Alkaloids/chemical synthesis , Guanidines/chemical synthesis , Phenylalanine/chemical synthesis , Alkaloids/chemistry , Animals , Anti-HIV Agents/chemical synthesis , Anti-HIV Agents/chemistry , Guanidines/chemistry , Phenylalanine/analogs & derivatives , Porifera/chemistry , StereoisomerismABSTRACT
The installation of the novel N,N-dimethylglycolamide ester auxiliary onto the C(1)-position of protected neuraminic acid donors allows for the exploitation of C(1)-neighboring group participation to generate sialoside conjugates with good to excellent alpha-selectivity under a variety of sialylation protocols, including those that would otherwise lead to nonselective or beta-selective sialoside products.
Subject(s)
Glycosides/chemical synthesis , Indicators and Reagents , Molecular Conformation , Neuraminic Acids/chemistry , StereoisomerismABSTRACT
[see structure]. The first synthesis of the trisaccharide fragment of the potent immunologic adjuvant QS-21A is reported. The key steps involve the application of sulfonium-mediated oxidative and dehydrative glycosidic couplings to construct the anomeric linkages in a short and convergent assembly of the branched trisaccharide.
Subject(s)
Adjuvants, Immunologic/chemical synthesis , Oligosaccharides/chemical synthesis , Saponins/chemical synthesis , Sulfonium Compounds/chemistry , Adjuvants, Immunologic/chemistry , Glycosylation , Oxidation-Reduction , Saponins/chemistry , Water/chemistryABSTRACT
[reaction: see text] Direct synthetic access to glycosyl-1-phosphates is accomplished with the dehydrative coupling of carbohydrate hemiacetals and dialkyl phosphates, employing dibenzothiophene-5-oxide and triflic anhydride. The procedure offers a new and versatile method for efficient preparation of a host of glycosyl-1-phosphates of variable structure with good control over anomeric selectivity.
Subject(s)
Sugar Phosphates/chemical synthesis , Glycosylation , Indicators and ReagentsABSTRACT
Nitrogen transfer to glycals: A new method for direct C2-aza-glycosylation with glycal donors has been developed (see scheme), employing the new reagent combination of thianthrene-S-oxide and trifluoroacetic anhydride for glycal activation, in an overall one-pot procedure.
